The Qatari government is failing to protect thousands of foreign domestic workers from exploitation and abuse, according to Amnesty International.

Fifty-two women told the human rights charity they had experienced gruelling employment conditions starkly different to those promised by recruitment agencies. Many said they were forced to work for 100 hours a week, had passports removed and their freedom of movement curtailed. In the worst cases, the women described serious physical and sexual abuse.

The conditions faced by women working for local and western expatriate families are so exploitative that some of them are victims of forced labour and human trafficking, Amnesty says. All except for three of the domestic workers questioned had their passports withheld by their employers, in breach of Qatar's sponsorship law.

Some workers also reported being physically and sexually abused, with one Indonesian woman showing researchers a deep scar on her chest where her employer had branded her with an iron. She was forced to work seven days a week despite being unpaid for months and was unable to flee because her employer banned her from leaving the house. When she did escape, she was picked up by the police and detained in a deportation centre.

Five days after the Guardian article on domestic-worker abuse in Qatar was published, the women said they had been freed from their contracts. Speaking on Tuesday, one woman said the group was awaiting payment for outstanding wages but hoped to be paid after a hearing at the interior ministry's human rights department.

Amnesty's director of global issues, Audrey Gaughran, said: "International attention on the 2022 Fifa World Cup has thrown a spotlight on the plight of migrant construction workers in Qatar. However, the complete absence of protections for domestic workers' labour rights and the fact that they are isolated in employer's homes, leaves them exposed to abuse to an even greater extent."

One of the main differences between the job as promised and the reality on arrival in Qatar is the long hours. LL, 26, who was employed by European nationals told Amnesty that she was forced to wake up at 3.30am and work until 10pm.

"The dog sleeps in the kitchen at night, so I have to clean the kitchen first thing in the morning, then I have to clean the yard outside," she said. "My employer wakes up at 5am, so at 4.30am I prepare breakfast. It's not what I was promised when I was recruited … when I got here the contract wasn't applied."

As well as the risk of being physically assaulted, three of the women who spoke to Amnesty said they had been raped by their employers. Researchers spoke to one domestic worker who broke her legs and fractured her spine when she fell from a window trying to escape sexual assault. She said her employer raped her as she lay injured and unable to move. Qatar's public prosecutor dismissed the case owing to a lack of evidence; her employer has never been held accountable for the allegations.

Campaigners say the law in Qatar too often punishes, rather than protects, the most vulnerable migrant workers. The penalty for rape in the kingdom is life imprisonment, but women who report any kind of sexual assault risk being charged with having illicit relations. And fear of being sent back to their home country deters many workers from seeking help.

In March 2013, more than 90% of the women detained by the authorities and awaiting deportation were former domestic workers. They may languish there for months, many without passports.

François Crépeau, the UN special rapporteur on the human rights of migrants, is presenting a report on workers' conditions in June. As part of his research he visited the deportation centre and discovered that most of the female detainees had been employed as domestic workers.

"When we were in the corridor, we started being surrounded by hundreds of people who wanted to talk to us. There's lots of people in all of those wards," he said. "It's all bunk beds everywhere, and plenty of them in each of the rooms we went in. We saw mattresses on the ground, in the rooms and in the corridor, water barely dripping from showers and all sorts of issues. Toilets were holes."

Amnesty is pushing for changes in the law relating to employment agencies in Qatar, so that workers do not end up in jobs where conditions differ radically from the original description. The report also calls for compulsory time off for domestic workers and a system allowing staff to lodge complaints with the labour ministry.

The article was amended on 23 April to reflect that the Filipina domestic workers who claim they were assaulted by their employers are awaiting a hearing at the interior ministry's human rights department and not Qatar's human rights committee, as originally stated.